Understanding the origin of new cells was a crucial step in developing the modern cell theory. Early scientists observed cells, but the mechanism of how life propagated at the cellular level wasn't initially clear.

Scientist Explaining Cell Division

The question asks about the scientist who explained that cells divide and new cells are formed from pre-existing cells. This specific contribution is a fundamental part of the cell theory and is attributed to a prominent German physician.

Let's look at the contributions of the scientists mentioned in the options:

• Theodore Schwann: He was a zoologist who, along with Matthias Schleiden (a botanist), formulated the initial cell theory in 1839. This theory stated that all plants and animals are composed of cells and that the cell is the basic unit of life. While crucial, their original theory did not fully explain how new cells arise.
• Rudolf Virchow: In 1855, Rudolf Virchow, a physician, added a significant point to the cell theory. Based on his studies of cellular pathology, he famously stated "Omnis cellula e cellula," which is Latin for "all cells come from cells." This principle asserted that new cells are produced only through the division of pre-existing cells. This directly addresses the question.
• Anton Van Leeuwenhoek: He was a pioneer in microscopy and is known for being one of the first people to observe and describe single-celled organisms (like bacteria and protozoa) and blood cells using his own meticulously crafted single-lens microscopes in the late 17th century. He observed living cells but didn't explain how they divide.
• Robert Hooke: In 1665, Robert Hooke observed thin slices of cork under his microscope. He saw small, box-like compartments that reminded him of the rooms (cells) in a monastery, and he coined the term "cell" to describe these structures. His observations were of dead plant cells, and he did not contribute to the understanding of cell division.

Based on these contributions, Rudolf Virchow was the scientist who provided the explanation that new cells arise from the division of pre-existing cells.

Comparing Contributions to Cell Theory

Rudolf Virchow's principle, "Omnis cellula e cellula", became a cornerstone of the modern cell theory, emphasizing that life does not arise spontaneously but is continuous through cell reproduction.

Revision Table: Cell Theory Contributors

Additional Information: Modern Cell Theory and Cell Division

The modern cell theory includes the original postulates by Schleiden and Schwann and the crucial addition by Virchow. It states:

1. All known living things are made up of one or more cells.
2. The cell is the basic structural and functional unit of all living organisms.
3. All cells arise from pre-existing cells through cell division. (This is Virchow's contribution)

Cell division is the process by which a parent cell divides into two or more daughter cells. This process is essential for growth, repair, and reproduction in organisms. The primary types of cell division are mitosis and meiosis.

• Mitosis: Occurs in somatic (body) cells and results in two genetically identical daughter cells. Important for growth and repair.
• Meiosis: Occurs in germ cells and is involved in the formation of gametes (sperm and egg cells). Results in four genetically different daughter cells with half the number of chromosomes of the parent cell.

Rudolf Virchow's observation provided the foundational understanding that these complex processes of cell division are the source of new cells in all organisms.